Electric switch



t ov m mu. w S t e N i N 0 S M 0 H T E (No Model.)

ELECTRIC SWITCH.`

No. 468,119. Patented Peb. 2, 1892.

2 Sheets-Sheet 2 `(No Model.)

E. THOMSON.

ELECTRIC SWITCH.

Patented Feb. 2, 1892.

UNITED STATES PATENT OFFICE.

ELIIIU THOMSON, Ol` LYNN, MASSACIIUSETTS, ASSIGNOR 'lO THF. THOMSON- HOUSTON` ELECTRIC COMPANY, Ol? (O.\'NE("I`I(`["1`.

ELCTRIC SWITCH.

SPECIFICATION forming partof Letters Patent No. 468,119, dated February 2, 1892, Application tiled July 14, 1890. Serial No. 358.708. No model) poorconductorof electricity-as, fot-instance, 5o a solution of a salt like sodium sulphate.

'lhc switch-arm C is provided with an operatiug-handle li andpivoted at I, where itis connected with the line-wire W'. A condncting-bar I) is carried u'pon one end of the arm 55 (i, and depcndingkthercfrotu is a series of metal-or conducting rods G, which dip into. the liquid when theswitch is`closed,as shown in Figyl. These bars may extend down so n as to touch the plate li, forming solid contact 6o therewith` or preferably the plate l; is con; structed with a trough-like lower edge T, in which is held a body-of mercury, into which the depending bars dip, as shown.

'lhe arrangement thus described consti- 65 .To all whom it may concern:

Be it known that I, ELmU THOMSON, a citizen of the United States, residingr at Lynn, in the county of Essex, State of Massachusetts,

5 have invented certain new and useful Improvements i-n Electric Switches, of which the following is a specification.

My present inventionaims to do away vith the difficulties often experienced in the presxo ent stateof electrical engineering where it is found desirable to open and close circuits on vwhich large currents of high potential are presen t. lVith the switches now in use it has been found that such circuits cannot be t5 opened and closed without the presence of, sparkinganddestrtyative arcs at the contacts.

Hy my switch, herein to be described, I find that it is possible to avoid all such arcing,and to control these large currents with ease and tutes the simplest torni of niyinvention; but

Lind it desirable -in most cases to place upon the mercury and under the fluid Fa number of small iron or other m'ctal balls, or they muy be replaced by hard carbon balls, or, better still, 7o the layer of iron balls niayhavea layerof carbon Yballs overlying them, thc relative specific gravities of the mercury, the iron and carbon balls, and the solution keeping them in position or preventing them ,from admixture. 75 Halls of a rounded forni are preferable; but I use this terni in a general sense, meaning small pieces, such that'the contact or con-Y tacts (i can readily pass through thcm,bring ing more or less into circuit. In this way it 8o will be seen that the different resistance-com ductors are arranged serially inthe order of their respective condnctivities and.for|n a path for the lnoving switch of gradually-increasing resistance as the switch is moved 85 from the closed position shown in Fig. 1 to the dotted-line position shown in Fig. 2.

Ou opening the switch the break in the circuit is not a sudden one` for the depending bars G tiret leave the mercury, then pass 9o through the iron balls, and then through the carbon balls and liquid, cutting eachinto circuit, and thereby gradually increasing the total resistance of the circuit until itis finally' broken by the Withdrawal of the bars entirely 95 from the liquid. In closing the switch the operation is the reverse, the resistance' be ing very great when the tuus are immersed in 2o perfectsafety to the apparatus used.

One form of the invention is' illustrated in the accompanying drawings, and it will be understood that in mechanical details this apparatuscan be niodiiied indefinitely, though 25 still'preserving the underlying principle upon which my invention is based, and which censists in general in causing theswitch-contacts to traverse successively a less and less pcrfeet conducting-path, so that the total resist- 3o ance of the circuit when the switch is opened is gradually increased until the switclrcontacts are entirely separated and the circuit ruptured. It is as though a closed path of practically no resistance between the switch- 3 5 contacts was gradually converted intoa path of higher and finally infinite resistance.

Figure 1 is a perspective view of the apparatus embodying my invention; and Fig. f3 is a side view of the same, showing by dotted 4o lines the switch in its open position.

In Fig. l, A is a receptacle of any desired and suitable form, made of insulating material, at one end' of which there is a plate '0f conducting material li, to which is con- 45 nectedawireor other conductor lV, forminga part of the line-circuit. The plate B extends down into the receptacle, and is therefore in contact with the (luid contained in the receptacle shown at F. '[liis fluid is a partial but the liquid, and beeomingfless and less until finally good electrical connection is estab` lished whenthe mercury in trough 'l` is reached. Both' opening.r and closing are so gradual as to he accomplished promptly, but without spark, on account of the grradation of resistancesprovided, whichgradation could not be obtained with thc use of rheostats or 4 l similar devices without enormous complication. The switch'is particularly useful where a currentv is 'to be interrupted, which is of great volume and in the path ot' which there` is .great self-induction,'giving rise to a tendency to maintain an arc on thcopeningot'the switch.

\Vhat I claim as new, and desire to secure Vby Lettere Patent, is,M

l. The combination o( the switch-contacts with a series of three or more conductors of different resistances brought into or cut eilt of A circuit serially by the switch when opening or the circuit, and, third, one or more conduct- 45eme-- ors of intermediate conductivity brought into or cut out of circuit during the openingor closure of the switch, as'set forth.

1i. 'lhe combination of the switch-contacts with balls of inferior conducting material located in thepath of the moving member of the switch and cut into and out of the circuit to form a path ot graduated resistance upon opening or closing the switch, as set forth.

4. 'lhe combination, in an electric switch,

ol' a receptacle containinga conductingdiquid of low conductivity in circuit witlrone ot the switch-eontacts,andballs of better conducting material through which passes the moving contact when opening or closing the cireu it, as set forth.

5. The combination of a receptacle containing,r a conducting-liquid of low conductivity, a trough-like plate B, containing a body of mercury forming one'of the switch-contacts, and halls of better conducting material located above said meren ry in the order of their respective couduetivities, with the moving switch-contact comprising a pin or pins passing down through said liquid int'o contact with the mercury.

' ELIIIU THOMSON.

\\'itnesses: Y Y

J OHN W. GxBBoNEY, GEORGE II. AL'roN. 

